The present invention relates to an infrared data communication module for performing data communication under so-called IrDa (Infrared Data Association).
An infrared data communication module for operation under IrDA is commonly used in the field of notebook personal computers, and recently, it is also used in a mobile phone or an electronic scheduler for example. Such an infrared data communication module includes an infrared LED, a photodiode and a modem circuit as enclosed in a single package for performing two-way wireless communication.
While the communication performance of the infrared data communication module is enhancing, there is an increasing demand for size reduction of the infrared data communication module. Moreover, dimensional accuracy is strictly required in manufacturing the infrared data communication module.
FIGS. 20 and 21 illustrate an example of prior-art method of making infrared data communication modules. According to the prior art method, use is made of a strip-like or rectangular substrate 1e on which plural sets of infrared light emitting elements 2e and infrared light receiving elements 3e are arranged in rows and then sealed in resin packages 4e. 
In such a method, the number of the resin packages 4e is the same as the number of the sets of light emitting elements 2e and light receiving elements 3e, so that each resin package separately encloses a respective set of light emitting element 2e and light receiving element 3e. After the resin-packaging, the substrate 1e is cut at positions indicated by phantom lines L1, L2, thereby providing a plurality of infrared data communication modules.
However, the above-described conventional manufacturing method has the following problems.
According to the conventional method, a resin package 4e is provided separately for each set of light emitting element 2e and light receiving element 3e. This leads to an increase in the total number of the resin packages 4e while also increasing the number of clearances 90 provided between the resin packages 4e, thereby wasting the space of the substrate 1e. As a result, the number of infrared data communication modules obtainable from the substrate 1e of a given size decreases, which leads to an increase in the manufacturing cost of the infrared data communication modules.
To solve the problem described above, the inventor of the present invention has previously conceived the idea of causing a single resin package to enclose, on the substrate 1e, a group of components including plural sets of light emitting elements 2e and light receiving elements 3e. With such a method, it is possible to minimize the number of the resin packages for eliminating the wasted space (clearances 90) between the resin packages.
With the above measure, however, the resin package comes into intimate contact with the substrate 1e over a large surface area. Therefore, in the case where the substrate 1e has a small thickness or is made of a relatively soft material, the substrate 1e warps, consequently distorting the infrared data communication modules obtained from the substrate.
Further, as shown in FIG. 22, use is made of mold members P1, P2 for molding a resin package 4e to seal a light emitting element 2e and a light receiving element 3e on a substrate 1e. Specifically, the head mold member P1 having a configuration for defining the configuration of the resin package 4e presses against the obverse surface of the substrate 1e, whereas the tail mold member P2 which has a flat pressing surface presses against the reverse surface of the substrate 1e. Then, with the tail mold member P2 held in intimate contact with the reverse surface of the substrate 1e, resin is injected between the head mold member P1 and the obverse surface of the substrate 1e for solidification into the resin package 4e. 
The substrate 1e is formed with through-holes 7 extending thicknesswise. The substrate 1e is further formed, on the reverse surface thereof, with terminals 71 connected to the through-hole 7, respectively. Since each of the terminals 71 made of a thin conductor film has a certain thickness, the reverse surface of the substrate 1e may become irregular. Therefore, the tail mold member P2 may not come into intimate contact with the substrate 1e, and the surface pressure against the reverse surface of the substrate 1e may be insufficient around the through-holes 7. As a result, a clearance may be formed between the reverse surface of the substrate 1e and the tail mold member P2. When resin is filled between the head mold member P1 and the substrate 1e in such a condition, the resin may flow via the through-holes onto the reverse surface of the substrate 1e. As a result, resin may be deposited on the reverse surface of the substrate 1e. 
Moreover, before the sealing step and the cutting step described above, a predetermined conductor pattern (not shown) and the terminals 71 are formed on the obverse and the reverse surfaces of the substrate 1e, respectively, by photolithography for example. Specifically, a resist material is applied on the substrate 1e which is initially formed with a copper film on a surface thereof. Then, a mask having a predetermined pattern disposed on the substrate which is then subjected to light exposure, development and etching for removing unnecessary portions of the copper film.
Then, an insulating layer (not shown) called xe2x80x9cgreen resistxe2x80x9d is formed on the substrate 1e to cover portions of the substrate other than the conductor pattern and the terminals 71 which are to be exposed. For forming such an insulating layer, a similar mask is utilized for light exposure. At this time, if the mask positionally deviates, the exposed area of the conductor pattern and the terminals 71 may become small.
An infrared data communication module A may be mounted on a module mounting board 9 so that the reverse surface of the substrate 1e extends perpendicularly to an obverse surface of the module mounting board 9, as shown in FIG. 23. In this case, the terminals 71 on the reverse surface of the substrate and a wiring pattern P formed on the module mounting board 9 are bonded together solder.
However, if the exposed portions for the terminals 71 are small as described above, solder fillets are not sufficiently formed or likely to be easily detached. Therefore, the terminals 71 of the infrared data communication module and the wiring pattern P of the module mounting board 9 are not reliably connected.
An object of the present invention is to provide a method of making an infrared data communication modules which is capable of eliminating or lessening the problems described above while also providing such an infrared data communication module.
In accordance with a first aspect of the present invention, there is provided a method of making infrared data communication modules comprising the steps of: forming predetermined wiring patterns on an obverse and a reverse surfaces of a substrate; mounting, on one of the surfaces of the substrate, a group of components including plural sets of light emitting elements and light receiving elements; resin-packaging the group of components mounted on the substrate; and dividing the resin-packaged components into a plurality of infrared data communication modules each of which includes a respective set of light emitting element and light receiving element; wherein the resin-packaging step comprises forming a plurality of mutually separated resin packages each of which collectively seals at least two sets of light emitting elements and light receiving elements.
According to this method, the number of the resin packages needed is smaller than the number of the sets of light emitting elements and light receiving elements. Therefore, the number of clearances provided between the resin packages can be reduced so that the total area of the clearances can be reduced. As a result, the number of infrared data communication modules obtainable from a single substrate is larger than is obtainable in the prior art, which leads to a cost reduction in manufacturing the infrared data communication modules.
Moreover, unlike the prior art in which a group of components mounted on a surface of the substrate is sealed in a single resin package, an appropriate number of clearances are provided between the plural resin packages, so that the surface of the substrate includes portions which are not held in intimate contact with the resin packages. Therefore, warping of the substrate due to the formation of the resin packages on one surface thereof can be reliably prevented or reduced. As a result, the produced infrared data communication modules are free from strains to provide a high quality.
Preferably, the mounting step includes arranging the plural sets of light emitting elements and light receiving elements in a matrix on said one surface of the substrate, and the resin-packaging step includes forming the packages so as to be arranged in a matrix.
According to the above, the substrate is less likely to warp both longitudinally and widthwise of the substrate. Therefore, it is possible to further enhance the quality of the infrared data communication modules finally obtained from the substrate.
Preferably, the substrate is elongated in one direction to be rectangular or strip-like. The substrate is formed with a plurality of slits extending widthwise of the substrate and spaced from each other longitudinally of the substrate. The group of components is mounted on said one surface of the substrate in each of regions defined between the slits.
According to the above, the substrate is likely to be warped longitudinally at the slits. Therefore, in resin-packaging the components mounted in a region between each two slits, even if a bending stress is applied to the substrate, such a stress is absorbed and alleviated by the deformation of the substrate at the slits. As a result, it is possible to prevent such a stress from largely affecting the adjacent region. Therefore, the substrate can be more reliably prevented from flexing at the regions on which the components are mounted.
Preferably, the pattern forming step includes forming, on the reverse surface of the substrate, terminals for connection to through-holes penetrating the substrate thicknesswise together with dummy patterns which are substantially equal in thickness to the terminals.
According to such a method, the dummy patterns formed on the reverse surface of the substrate to have substantially the same thickness as the terminals connected to the through-holes provides a sufficient surface pressure when the substrate is compressively held by a mold. Therefore, the dummy patterns held in firm contact with the mold on the reverse surface of the substrate prevents resin, which enters into the through-holes from the obverse surface of the substrate, from flowing out onto the reverse surface of the substrate.
Preferably, the pattern forming step includes forming, on the reverse surface of the substrate, terminals for connection to through-holes penetrating the substrate thicknesswise. The terminals are elongated to be substantially rectangular for bonding to an external mounting board.
When an insulating layer is formed on the reverse surface of the substrate, by photolithography for example, in such a manner as to expose the terminals, the mask for light exposure may be disposed at a deviated position. However, since the terminals are elongated into a generally rectangular configuration according to this method, such a deviation may be allowed longitudinally of the terminals. Further, the elongated terminals provide a sufficient area utilized for effectively bonding to an external module-mounting board.
In accordance with a second aspect of the present invention, there is provided an infrared data communication module made by the steps of: forming predetermined wiring patterns on an obverse and a reverse surfaces of a substrate; mounting, on one of the surfaces of the substrate, a group of components including plural sets of light emitting elements and light receiving elements; resin-packaging the group of components mounted on the substrate; and dividing the resin-packaged components into a plurality of infrared data communication modules each of which includes a respective set of light emitting element and light receiving element; wherein the resin-packaging step comprises forming a plurality of mutually separated resin packages each of which collectively seals at least two sets of light emitting elements and light receiving elements.
The structure described above provides the same advantages as the first aspect of the present invention.
Preferably, the substrate may be formed with through-holes penetrating the substrate thicknesswise, and the reverse surface of the substrate may be formed with terminals for connection to the through-holes and dummy patterns which are substantially equal in thickness to the terminals.
Preferably, the obverse surface of the substrate may include sub-areas each for mounting a respective set of light emitting element and light receiving element, and the wiring patterns may be formed respectively in the sub-areas. The dummy patterns may correspond in position and in general configuration to the wiring patterns.
According to this structure, the wiring patterns having a certain thickness are formed at the sub-areas on the obverse surface of the substrate, whereas the dummy patterns having a corresponding thickness are formed on the reverse surface of the substrate in corresponding relation to the wiring patterns. Thus, the surface pressure applied by the mold are sufficiently increased so that the substrate and the mold are held in intimate contact with each other. As a result, the sub-areas can be reliably sealed with resin to reliably produce infrared data communication modules at respective sub-areas.
Preferably, the substrate may be formed with through-holes penetrating the substrate thicknesswise. The reverse surface of the substrate may be formed with terminals for connection to the through-holes and for bonding to an external mounting board. The terminals may be elongated to be substantially rectangular.
According to this structure, a solder fillet can be formed in an amount sufficient for strongly soldering each terminal on the reverse surface of the substrate to the wiring pattern on the module mounting board. Therefore, it is possible to increase the mounting strength of the infrared data communication module on the module mounting board.
Preferably, the terminals maybe so formed as to projects from an obverse surface of the mounting board when the substrate is mounted on the mounting board with the reverse surface of the substrate oriented perpendicularly to the obverse surface of the substrate.
Since the wiring pattern on the module mounting board has a predetermined width, there is a limitation on enlarging the terminals on the reverse surface of the substrate longitudinally thereof. However, it is possible to extend the terminals perpendicularly to the obverse surface of the module mounting board as much as possible the width of the substrate allows. Therefore, with the above-described structure, it is possible to form a sufficient amount of solder fillet.